Polyester compositions stabilized with p-benzoquinone



Patented Mar. 24, 1953 POLYESTER COMPOSITIONS STABILIZED WITHP-BENZOQUINONE Thomas F. Anderson, Huntsville, Ala.,

Libbcy-Owens-Ford Glass Company,

assignor to Toledo,

Ohio, a corporation of Ohio No Drawing. Application February 23, 1950,Serial No. 145,913

1 Claim.

The invention relates to stabilized thermosetting compositions, and moreparticularly to stabilized thermosetting compositions containing apolymerizable unsaturated alkyd resin.

A polymerizable unsaturated alkyd resin (1. e.. a polymerizableunsaturated polyhydric alcoholpolycarboxylic acid polyester) is highlyadvantageous as a starting material for the production of hardenedsynthetic resins in that it is resinous in character beforepolymerization, and is fusible at a temperature at which polymerizationis not rapid. Other heat-hardenable compositions. such asurea-formaldehyde and phenol-formaldehyde compositions, are much moredifficult to fabricate because they do not exist as plastic resins attemperatures much below their hardening temperatures. Since aheat-hardenable composition can be shaped only while it is in a fusedcondition, the failure of other heat-hardenable compositions to reach afused state below their hardening temperatures is a great handicap infabricating operations. By the time a ureaformaldehyde orphenol-formaldehyde composition has reached a fused state in afabricating operation, its hardening already has begun, so that thehardening interferes with the shaping or molding of the composition.

A saturated heat-hardenable alkyd resin, such as glycerol phthalate, ishardened by esterification with elimination of water. that is hardenedby esterification cannot be employed to make a molded article or othersolid body, because it is too difficult to remove water from theinterior of such a solid body in order to complete the hardening. Evenurea-formaldehyde and phenol-formaldehyde compositions tend to give offsmall amounts of volatiles as they are hardened in a mold. In contrast,a polymerizable unsaturated polyester hardens by polymerization withoutevolution of volatiles.

These important advantages have made polymerizable unsaturatedpolyesters of great commerical value; nevertheless the commercializationof such polyesters has been seriously impeded by the fact that suchpolyesters lack stability after the addition of the polymerizationcatalyst that is necessary to cause polymerization to take place. a Inthe manufacture of commercial products from such polyesters,polymerization in the presence of a polymerization catalyst ordi- Analkyd resin narlly is carried out at an elevated temperature in order tocause the polymerization to take place rapidly. After the addition of apolymerization catalyst to such a polyester, however, polymerizationproceeds slowly at atmospheric temperatures. The rate of polymerizationat atmospheric temperatures after the incorporation of a polymerizationcatalyst is rapid enough so that in a few days the polyester may becomea substantially infusible, worthless mass that can-- not be formed intoany useful product.

The useful life of a polymerizable unsaturated polyester afterincorporation of a polymerization catalyst is so short that it does notafford suffi cient time for a manufacturer to ship thecatalyst-containing polyester to a user. For that reason it was formerlythe practice for the manufacturer of a polymerizable unsaturatedpolyester to ship the polyester without incorporating the polymerizationcatalyst, so that it was necessary for the user of the polyester to addthe required proportion of the catalyst just before the polyester wasused. The minute proportion of a polymerization catalyst required for a.small batch of the material must be weighed out very accurately, thenincorporated very uniformly throughout the batch. Uniform incorporationof a catalyst in a solid material such as molding composition is aparticularly difficult operation and requires very expensive equipment.

Certain inhibitors" for the polymerization of unsaturated polyesters areknown. It has been found, however, that the addition of such aninhibitor to a mixture of a polymerizable unsaturated polyester and apolymerization catalyst has no better effect than the omission of partof the polymerization catalyst from the mixture. The addition of such aninhibitor not only retards the polymerization of the mixture atatmospheric temperatures to the same extent as the polymerization wouldhave been retarded by omission of a certain proportion of thepolymerization catalyst from the mixture, but also interferes with thepolymerization at molding temperatures, particularly after the materialhas been stored for a few days, so as to impair the quality of themolded product to the same extent as the quality would have beenimpaired if that same proportion of the polymerization catalyst had beenomitted. These inhibitors are of no value for the purpose ofstabilization, because it is useless to add an inhibitor when exactlythe same effect can be obtained by omitting part of the polymerizationcatalyst. Certain substances are known which, in conjunction withoxygen, have the effect of greatly retarding the polymerization atatmospheric temperatures of a mixture of a polymerizable unsaturatedpolyester and a polymerization catalyst, without producing acorresponding impairment of the quality of the molded 'product. (Suchsubstances are referred to as stabilizers" to distinguish them from ordinary inhibitors.) However, the stabilizing effect in that case is thecombined eiiect of oxygen and the stabilizing substance. The stabilizineffect is not produced by such a substance alone, but requires thepresence of oxygen. Therefore, in order to stabilize a mixture of ,apolymerizable unsaturated polyester and a polymerization catalyst bymeans of such a substance, it has been necessary to prepare thecomposition, containing such a substance, in a physical form such thatthe composition is thoroughly permeated by air.

In many applications it is inconvenient or inipractical to maintain acomposition containing a polymerizable unsaturated polyester (which isordinarily a liquid) and a polymerization catalyst in such physical formthat it is thoroughly permeated by air, but no substances have beenknown to retard the polymerization of such a composition at atmospherictemperatures without producing a corresponding impairment of the qualityof the molded product, except certain substances that produce sucheffect only so long as the composition is thoroughly permeated by air.

The principal object of the invention the bilization of a mixture of apoly s zable unsaturated polyester and a. polymerization cciaiystwithout the nec ssity of keeping the car .i tion permeated by air. Morespecific cbjcr advantages are apparent from the following (1escription,which illustrates and discloses but is not intended to limit the scopeof the invention.

The present invention is based upon the discovery that a certainsubstance has the effect of greatly retarding the polymerization atatmospheric temperatures of a mixture of a polymerizable unsaturatedpolyester and a polymerization catalyst, even while air is excluded fromthe mixture, without producing a corresponding impairment of the qualityof the molded product. The fact that the stabilizing effect obtained inthe practice of the invention does not require the presence of oxygenhas been demonstrated as follows:

One of the stabilizers heretofore used (0.2 gram of guaiacol) and apolymerization catalyst (3.0 grams of benzoyl peroxide) were mixedintimately with 100 grams of a polymerizable unsaturated polyester andgrams of diallyl phthalate (an unsaturated substance that is capable ofcopoly merizing with the unsaturated polyester), and the resultingviscous liquid was mixed with 180 grams of asbestos fiber in a Banburymixer. The resulting mixture was removed from the Banbury mixer in theform of a solid lump about two inches in diameter. After standing forthree weeks at atmospheric temperature, the lump of material hadpolymerized to a worthless mass. Thus it was demonstrated that thestabilizing effect is not produced by this known stabilizer alone in theabsence of oxygen.

The procedure described in the preceding paragraph was repeated, but inthis case the u'aiac'ol was replaced by an equal amount of benzoquinon(a stabilizer of the present invention). At the end of three weeks, thecomposition was still fusibio and could be molded into useful articlesunder heat and pressure.

Since a stabilized thermosetting molding composition embodying theinvention does not require the incorporation of a catalyst by the user.it can be used by small fabricators who have no equipment forincorporating a catalyst in a molding composition, and dahbe timeQaconomically by large fabricators than ai'nateri'al requiring theaddition of a catalyst by the user.

A composition embodying the invention comprises (1) a pol'ym'erizableunsaturated polyhydric alc'chol-polycarboxylic acid polyester; (2) acatalyst of the class consisting of organic peroxides andorganicozonides; and (3) as an agent for increasing the stability of thecomposition at atmospheric temperatures without proportionatelydecreasing the curability of the composition, p-benzoquinone.

Preferably the composition also contains a polyzncrizable unsaturatedmonomeric substance. The properties of finished articles produced bypolymerization of a composition embodying the invention are betterwhen'thec'ompo'sition contains a polymerizable, unsaturated monomericsubstance, so that such asubstance is ordinarily used in thecomposition. It is believed that pecause of their large size thepolyester molecules are not mechanically well adapted to polymeriziwithone another andtha't'th'e better propertir. of finished articlesproduced from ab'ompositic; containing a 'polymei'izable unsaturatedihdn. ineric compound are due to the"superior curbility of such acomposition. Ihe monomeric compound is believed to impart bettercurablliiy to the composition because of its ability to cross link theunsaturated polyester molecules by copolymerizing with such molecules.

STABILIZER A stabilizer of the invention increases the stability atatmospheric temperatures of a composition comprising a polymerizableunsaturated polyester and a catalyst, without proportionately decreasingthe curability of the composition. The stabilizer in a compositionembodying the invention is p-benzoquinone,

Hydroquinone, unlike the substances of the'pbenzoquinone serieshereinbefore described, does not act as a stabilizer in atherinos'etting composition comprising a polymerizable unsaturatedpolyhydric alcohol-'polycarboxylic acid polyester and a catalyst of theclass consisting of organic peroxides and organic ozonides, as ishereinafter demonstrated.

CATALYST A stabilized therm-os'etting compositionof-the inventioncontains a catalyst of the class consisting of organic peroxides andorganic ozonides. which is essential for rapid polymerization of thecomposition at molding temperatures. The term organic peroxides"includes compounds having the general formula wherein R is alkyl,aralkyl, acyl, or hydroxysubstituted or halo-substituted alkyl, aralkylor acyl, and Y is hydrogen or is of the same class as R.

Acidic peroxides in which Y and R are acyl or hydroxyor halo-substitutedacyl, which may be used as catalysts in the practice of the inventioninclude: bis(benzoyl)peroxide, bis(p-br0mobenzoyl) peroxide,bis(phthalyl) peroxide, bis(p chlorobenzoyl) peroxide,bis(dichlorobenzoyl) peroxide, bis(succinyl) peroxide, acetyl benzoylperoxide, bis(acetyl) peroxide and bis(chlorcacetyl) peroxide.

Peroxy acids in which R is acyl and Y is hydrogen, and peroxy acidesters in which R is acyl and Y is alkyl or aralkyl, which act as curingcatalysts in the present invention, include peracetic acid, perbenzoicacid, t-butyl perbenzoate and benzyl peracetate.

Hydrogen peroxides in which R is alkyl or aralkyl and Y is hydrogen,which act as curing catalysts in the present invention, include t-butylhydroperoxide.

Organic ozonides which may be used as curing catalysts in the practiceof the present invention include diisopropylene ozonicle anddiisobutylenc ozonide.

Mixtures of organic peroxides and organic ozonldes may also be used asthe curing catalyst,

Organic peroxides in which R is benzoyl or halosubstituted benzoyl suchas benzoyl peroxide (i. e., bis(benzoyl) peroxide), bis(p-chlorobenzoyl)peroxide, bis(pbromobenzoyl) peroxide, bis(dichlorobenzoyl) peroxide,and t-butyl perbenzoate, are very eifective in the production of moldedproducts having good cured quality.

Futures A stabilized thermosetting composition of the invention maycontain a filler. The filler may be an organic filler (i. e., a fillerfrom a vegetable or animal source) or an inorganic or mineral filler.Organic fillers which may be used include alpha cellulose, which is thepurest and lightestcolored organic material ordinarily available andcotton linters. Inorganic or mineral fillers which may be used includefibrous fillers such as glass fiber or asbestos, and non-fibrous fillerssuch as ground glass, clay, mica, talc or calcium silicate.

POLYMEBIZABLE UNSATUBATED POLYESTER Any unsaturated polyester that ispolymerizable into an lnfusible resin at ordinary molding temperatures,o any mixture of such materials with one another or with one or moreother materials which may or may not be polymerizable, may be used inthe practice of the present invention. The polymerizable unsaturatedpolyester may be a limpid liquid 01. very low viscosity, or a tacky,viscous liquid, or may be of any consistency depending upon thematerials used in its preparation and the degree to which they arereacted.

A polymerizable unsaturated polyhydric alcohol-polycarboxylic acidpolyester used in the practice of the invention is prepared by reactionof one or more polyhydric alcohols and one or more polybaslc acids. Theproportion of polyhydric alcohols having more than two hydroxy groups,such as glycerol or pentaerythritol, and the proportion ofpolycarboxylic acids having more than two carboxy groups, such as citricacid, preferably is small so that in the production 6. of the polyesterthere may be maximum esteriflcation of the hydroxy and carboxy groupswithout attainment of excessive viscosity (i. e., throughcross-linking). Ordinarily it is desirable that the unsaturatedpolyester be polymerizable into an infusible or high melting pointresin. so that the proportion of unsaturated components should be suchthat the polyester contains an average of more than one double bond permolecule (for example, there may be an average of eleven or more doublebonds in every ten molecules oi the polyester) and for the purposes ofthe instant invention it is to be understood that the term unsaturatedpolyester" means a polyester that is polymerlzable into an infuslble orhigh melting point resin.

The present invention is applicable to all polymerizable unsaturatedpolyhydric alcohol-polycarboxylic acid polyesters. A typical example 01'such a polyester is a product prepared by the reaction of an unsaturateddicarboxylic acid such as maleic, fumaric, itaconic, cltraconic ormesaconic acid with a dihydric alcohol such as any polymethylene glycolin the series from ethylene glycol to decamethylene glycol, propyleneglycol, any butylene glycol, any polyethylene glycol in the series fromdiethylene glycol to nonaethylene glycol, dipropylene glycol, anyglycerol monobasic acid monoester (in either the alpha or betaposition), such as monoformin or monoacetin, any monoether of glycerolwith a monohydric alcohol, such as monomethylin or monoethylin, or anydihydroxy alkane in which the hydroxy radicals are attached to carbonatoms that are primary or secondary or both, in the series fromdihydroxy butane to dihydroxy decane.

Part of the unsaturated dioarboxylic acid may be replaced by a saturateddicarboxylic acid, such as any normal acid in the series from oxalicacid and malonic acid to sebacic acid, or any benzene dicarboxylic,naphthalene dicarboxylic or cyclohexane dicarboxylic acid, ordiglycolic, dilactic or resorcinol diacetic acid. All of the unsaturatedacid may be replaced by a saturated acid if a polyhydric alcohol ispresent whose molecule has two or three free hydroxy groups and consistsof an ether of one or two molecules of allyl or methallyl alcohol withone molecule of a polyhydroxy compound such as glycerol, pentaglycerol,pentaerythritol, butantetrol-l, 2, 3, 4, a trihydroxy normal alkanehaving from four to five carbon atoms such as butantriol-l, 2, 3 or amonoalkyl ether of pentaerythritol or butantetrol-l, 2, 3, 4 in whichthe alkyl radical has from one to four carbon atoms and has from one totwo hydrogen atoms attached to the same carbon atom as the etherlinkage, such as the monomethyl or monoisobutyi ether ofpentaerythritol.

In the practice of the invention the preferred polymerizable unsaturatedpolyhydric alcoholpolycarboxylic acid polyesters are the so-called"linear polyesters, i. e., those which have very little cross-linking inthe polyester molecules, as evidenced by the .fact that such polyestersare soluble in solvents such as acetone. Such polyesters are formedmainly by esteriflcation of a dihydrie alcoholand a dibasic acid. Ofcourse, such polyesters are really only substantially" linear since itis not possible to avoid all crosslinking, at least through theunsaturated bonds in the polyester molecules. In fact, a linear (orsubstantially linear) polyester may be obtained .even though in thepreparation of such polyester a small proportion of the dihydric alcohol(e. g., less than about. 5. mol percent of .thealcohol) .ls

a'csa'rsa replaced 'by a polyhydric alcohol containing more than twoalcohol radicals, "such as glycerol or pentaerythiltol, or a smallproportion oi the dibasic acid (e. g., less than about mol per cent ofthe acid) is replaced by a polybasic acid containing more than Ztwo acidradicals, such as citric acid. The preferred linear polyester for use inthe practice of the invention is prepared by carrying out theesterifica'tldn reaction substantially to completion -'(i. e.. to anacid number of less than about 40) Without permitting substantiaq-(addi-tion-) polymerization to take place. Although the esterificationreaction is usually carried out under an inert gas atmosphere so as toexclude oxygen, various inhibitors may be used to prevent appreciablepolymerization of the polyester during the esteriflcation reaction.

in the preparation of the polymerizable unsaturated polyester, any ofthe usual modifiers such "as monobasic acids, monohydric alcohols andnatural resin acids maybe added. The larger the proportions oi monobasicacids and monohydric alcohols. the IOWuI is the average number of acidand alcohol residues 'in the resulting polyester molecules, and thelower is the viscosity of the polyester. "On the other hand, the morenearly equal the molecular proportions of dibasic acid and dihydricalcohol. the :greater is the average number of residues in the resultingpolyester molecules, and the greater is the viscosity. The proportionsof ingredients used are those proportions that produce a polymerizablepolyester of the desired viscosity. Other properties of the polyester,such as solubility in various solvents. also may 'be varied by selectingvarious reacting ingredients and varying their proportion. Theinfusibility, 'hardness and inertness of the product obtained bypolymerization of the polyester may be increased by varying the initialreacting ingredients to increase the average number of double bonds .permolecule of the polymcrizabie polyester.

The point to which the reaction of the ingredients is carried in thepreparation of the polymerizablepolyestcr is simply that point at whichthe product has the desired properties. The consistency or viscosity ofthe polyester varies directly with the average number of acid andalcohol residues in the molecule. For example, the average number ofresidues in the molecule of the polyester may vary from about three toabout one hundred twenty.

If desired, the-reaction may be expedited by use of an acid substance asa catalyst. Any organic acid, inorganic acid or acid salt that issoluble in the reaction mixture may be employed as a catalyst, but it isdesirable that any acid substance used be readily volatile or be of sucha character that it has no deleterious effect in the final product. Theamount of acid catalyst employed is simply that amount which acceleratestheesterification to the desireddegree.

The reaction is carried out at a temperature high enough and for a timelong enough .to secure the desired consistency. An elevated temperaturepreferably is employed to expedite the reaction, but during thepreparation of the polyester, the'temperature should not be so'high northe time of reaction so-long as to cause substantial polymerization.Thercis less danger of prematurepolymerization if an inhibiting agent isadded before'the esterification is carried out.

"Whenever added, an inhibiting agent is used in the proportion requiredto give the desired degree iii-inhibiting eflect. -It ma'y be necessaryto use different inhibitors in widely different proportions in order tosecure the same inhibiting efiect.

Any desired inhibitor such as hydroquinone, pyrogallol, tannic acid orany aromatic amine, such as aniline or p'henylene diamine may beemployed as an inhibitor.

The preparation of the unsaturated polyester preferably is carried outin an atmosphere of an inert gas such as carbon dioxide, nitrogen 'orthe like, in order to prevent darkening or to make 'it possible toobtain a pale or colorless product. Bubbling the inert gas through thereacting ingredients is advantageous in that the gas .serves the addedfunctions of agitation and of expediting th removal of water formed bythe reaction. Exclusion of oxygen is desirable not only because itcauses discoloration, but also because it tends to produce prematurepolymerization at the elevated temperatures used.

The acid number of the product depends upon the degree ofreaction-and'the proportions of acid and alcohol used for the reaction.With equimolecular proportions of dibasic acid and dihydric alcohol, thereaction may be carried to an acid number of about 20. The use of anacid catalyst may make it possible'to attain a lower acid number withoutsubstantial polymerization.

A polymerizable polyester may be prepared by the following procedure:

5.4 mols of maleic anhydride and 5.4 mols oi diethylene glycol are mixedtogether in a threenecked flask. The flask is then fitted with athermometer, a tube leading to a condenser and an inlet tube throughwhich is introduced a moderate stream of carbon dioxide. and is loweredinto an-oil bath at a temperature of 210 C. Dur ing the subsequentreaction the distillate may be analyzed, and a sufficient amount of theingredient lost in excess may be added to the flask from time to time tomaintain the initial proportions of reacting ingredients. If the onlyaddition is a sufiicient amount of the ingredient lost in excess tomaintain the initial proportions, the rate of removal of um'eactedingredients gradually decreases and substantially no unreactedingredients may be left in the composition at the end of the reaction.After 8 hours at such temperature, a polyester is obtained in the formof a stiff liquid havingan acid number of 18. If ethylene glycol weresubstituted'for the diethylene lycol in the foregoing procedure, itwould be diiiicult to reduce the acid-number below-40 without causingpolymerization, and the product wouldbe a very thickgum.

Alternatively, this first procedure, as described in the foregoingparagraph, may bee'mp'loyed-except that 1.5 instead of 5.4 mols ofmaleic anhydride and 1.5 instead of 5.4 mols of diethylene glycol areused together with an-amount of hydroquinone equal to .02 percent of thereacting ingredients; and reaction is continued 'for 6% hours. Theresulting polyester is a moderately stiff liquid :having an acid numberof '11.

--A further procedure that may 'be used is the same as the firstprocedure except that 2 instead of 5.4 mols of maleic anhydride and 2.1instead of 5.4 mols of diethylene gl-ycol are used; and the reaction iscarried out for 4 hours to produce a still liquid having an acid numberof 14.

Another type of polymerizable polyester may be prepared by a procedurethat is the same as the first procedure except that 3 instead of 5.4mols of 'maleic anhydride and 3.3 instead of 5.4 mols o1 diethyleneglycol are used togetherwith an amount :of hydroquinone-equal to 509 percent of the reacting ingredients and an amount of p-toluene sulfonicacid equal to 0.18 per cent of i the reacting ingredients; and thereaction is carried out for four hours at 200 C. to produce a stiffliquid having an acid number of 10.6.

As a further alternative. the first procedure may be employed exceptthat 6 instead of 5.4 mols of maleic anhydride are employed; thediethylene glycol is replaced by 6 mols of ethylene glycol; a slowerstream of carbon dioxide is used; and the ingredients are kept in an oilbath at 220 C. for hours. The resulting polyester is a very thick gumhaving an acid number of 53.

A polymerizable polyester may also be prepared by a procedure that isthe same as in the preceding paragraph except that the maleic anhydrideis replaced by 5 mols of fumaric acid; the ethylene glycol is replacedby 5 mols of diethylene glycol; and the reaction is continued for 8%hours. The resulting polyester is a stiff liquid having an acid numberof 23. If in the foregoing procedure the diethylene glycol were replacedby an equimolecular proportion of ethylene glycol and half of thefurnaric acid were replaced by an equimolecular proportion of phthalicanhydride, the product would be a hard brittle solid. The substitutionof fumaric acid for maleic anhydride increases the length of timerequired to reach a given acid number at a given temperature. of an acidcatalyst upon the esterification is greater when iumaric acid is used.When fumaric acid is employed, other conditions being the same, theresulting polyester tends to be more viscous and greater care isnecessary in order to prevent premature polymerization.

As a further variation the first procedure may be used except that themaleic anhydride is replaced by 1.5 mols of fumaric acid; 1.5 instead of5.4 mols of diethylene glycol are employed; and the temperature isvaried between 200 and 220 C. After the reaction has been continued for2 hours, the acid number is '73. After 6 hours, the product is a stiffliquid having an acid number of 41.

A polymerizable polyester may also be prepared by a procedure that isthe same as that of the preceding paragraph except that p-toluenesulfonic acid (1.5 grams) is added to the initial ingredients; andreaction for only 2 hours in stead of 6 hours is required to produce astill liquid having an acid number of 41.

A procedure that may also be used is the same as that of the next to thelast paragraph except that the fumaric acid is replaced by 3.3 mols ofmaleic anhydride; 3.0 instead of 1.5 mols of diethylene glycol are used;1.5 grams of p-toluene sulfonic acid and 1.3 grams of hydroquinone areadded to the initial ingredients; and the reaction is carried out for 3hours to produce a limpid liquid having an acid number of 26.

A polymerizable polyester may be prepared by a procedure that is thesame as the next to the last paragraph except that 3 instead of 1.5 molsof iumaric acid and 3.3 instead of 1.5 mols of diethylene glycol areused; and the reaction is carried out for 3 hours at temperaturesranging from 200-210 C. to produce a stiff liquid having an acid numberof 12.

A further procedure that may be used is the same as thatof the next tothe last paragraph except that the hydroquinone is omitted; and reactionfor 5 hours is required to produce a stiff liquid having an acid numberof 28.

Another procedure that may be used is the However. the acceleratingefiect same as the'procedure of the next to the last paragraph exceptthat the weight or p-toluene sulfonlc acid is equal to 0.18 per cent oi.the weight of the reacting ingredients; an amount of hydroquinone equalto 0.09 per cent of the reacting ingredients is added at the start ofthe reaction; and reaction is carried out at 200 C. for 5 hours toproduce a still liquid which has an acid number oi 10.1.

MoNoMEns Although a polymerizable unsaturated polyester may be usedalone as the polymerizable cross linking straight chain polyestermolecules.

The combination of the polyester and the monomeric compound usuallypolymerizes more rapidly than either of such substances alone. When usedin the proper proportions the monomer improves the Water resistance andinsolubility of the final product.

A polymerizable unsaturated monomeric substance used in the practice ofthe present invention may be any substance (or mixture of suchsubstances) whose molecule contains at least one polymerizable ethylenicdouble bond that is capable of copolymerizing with a polymerizableunsaturated polyhydric alcohol-polycarboxylic acid polyester. Thepolymerizable ethylenic double bond or plurality of polymerizableethylenic double bonds may be contained in radicals of unsaturatedacids, such as maleic, fumaric. citraconic and mesaconic acids, or inother unsaturated radicals such as vinyl, allyl and crotyl radicals.These unsaturated radicals may be connected directly to carbon atoms inthe molecule, or may be connected to the rest of the molecule by ester,ether or amide linkages.

A polymerizable unsaturated monomeric substance whose molecule containsonly one poly merizable ethylenic double bond may be a vinyl compoundsuch as styrene, or p-methyl styrene, 2,4-dimethyl styrene, 2,3-dimethylstyrene. 2,5- dimethy] styrene, isopropenyl toluene, vinyl naphthalene,vinyl benzoate, vinyl dibenzofuran or acrylonitrile; or an alkyl esteror the amide of a monobasic acid whose molecule contains one ethylenicdouble bond or the aldehyde corresponding to such an acid, such asmethyl acrylate,

methyl methacrylate, isobutyl methacrylate. methacrolein, acrolein,acrylamide, methacrylamide, crotonaldehyde. or cinnamaldehyde; or anester of a monobydric alcohol whose molecule contains one ethylenicdouble bond with a saturated monobasic acid, e. g., allyl lactate orcrotyl glycolate.

A polymerizable unsaturated monomeric substance whose molecule containstwo or more poly v merizable ethylenic double bonds may be an ester of amonohydric alcohol whose molecule contains one polymerizable ethylenicdouble bond with a monobasic acid whose molecule contains onepolymerizable ethylenic double bond (e. g., allyl acrylate or allylmethacrylate); or an ester or 'mixed ester of a. molecule of a saturateddihydric alcohol with two molecules of a monobasic acid whose moleculecontains one polymerizable ethylenic double bond (e. g., ethylenedimethacrylate, triethylene dimethacrylate, propylene dimethacrylate,hexamethylene dimethacrylate);

or an ester or mixed ester of two alcohol mole- 2,032,703 13 14 TableI-Continued Bebwic acid Benzene dicarborylio acid" Biphenyldlcsrboxylioacid Naphthalene dicarboxylic acid.

i i Pyrotartaric acid HO-CCHCH;-C0H

0H Phenyl phosphonic acid -O --P\ boxy group may have the generalformula includes 0-, m-, and p-phthalic acid. Similarly. F-OH, in whichF is the acid radical of acrylic. the enclosure of the biphenyl ring andthe naphmethacrylic, or alpha-chloracrylic acid, or may thalene ring inparentheses in the above table is have the general formula, R-O-D-OH, inintended to indicate that any of the various powhich R is methyl, ethyl,n-propyl, isopropyl. sition isomers may be used. In the case ofcyclonbutyl, isobutyl, secondary butyl or tertiary hexane dicarboxylicacid, any of the various pobutyl, and D is the divalent acid radical ofany sition isomers may be used either in cis or in trans of the firstnine dibasic acids listed in Table L relationship. When R. in the lattergeneral formula is allyl.

The polymerizable unsaturated monomeric sub crotyl, alpha-methyl allyl,methallyl, beta-chloro stance may also be an ester of a molecule ofallyl or beta-methyl crotyl, D may be the dione of the dibasic acidslisted in Table I with valent acid radical of any of the dibasic acidsOne molecule of a saturated monohydric alcohol listed in Table I. suchas methyl, ethyl, n-propyl, isopropyl, 4D The substance having analcoholic hydroxy n-butyl, isobutyl, secondary butyl or tertiary groupmay consist of a compound having the butyl alcohol or cellosolve and onemolecule of general formula one of the unsaturated monohydric alcoholshereinbefore described.

The polymerizable monomeric compound may also be an ester or mixed esterof a molecule of a tribasic or other polybasic organic or inorganic acidwith three or more monohydric alcohol molecules each having apolymerizable ethylenic double bond. Such monomeric compounds includetriallyl tricarballylate, triallyl aconitatc, triallyl citrate, triallylphosphate, trimethallyl phosphate, triallyl cyanurate, andtetrallylsilicate.

The polymerizable monomeric compound m y also consist of an ester of twosubstances that will be described, one of which has a carboxy group andthe other of which has an alcoholic "Benzene dicarboxylic acid in theforegoing table in which R is the monovalent hydrocarbon radical ormonovalent chlorinated hydrocarbon radical of any of the alcohols listedin Table 11. below, and in which B is methylene, methyl methylene, orany phenylene radical. Th substance having an alcoholic hydroxy groupmay also consist of a compound having the general formula R-O-D-O-EOH inwhich D is the divalent acid radical of any of the dibasic acids listedin Table I. R has the same significance as in the preceding generalformula and E is the divalent radical to which two hydroxy groups areattached in any of the dihydroxy hydroxy group. The substance having acarcompounds listed in Table III below.

Table I I Ally] alcohol CHi=CH-CH;-0H Grotyl alcohol orb-c H=CHGH|-O HCHI Alpha-methyl allyl alcohol CH|=OH-H-0H CH. Methallyl alcoholCHg=7-OHg-OH 0| Beto-ohioro ally! alcohol CH,=. J-'CH O H Beta-methylorotyi alcohol CHCH=l-CH,-O H

1 Table In Ethylene glycol H0-CH;CH:OH

OH Propylene glycol CH -(IHOH,-OH

OH 1,2-butylene glycol HO-CH:( HOH|0H| OH OH 2.3-butylene glycolCEh-QIH-(EB-Glih 'Iri-mothylone glycol H O CH) :O H

Tetra-methylene g]ycol... l H O -(CHI)('0H Penta-methylene glycol HO(CH),-0H

Hem-methylene glycol ElO-(Clfih-OH Hepta-methylcne glycoL.llO-(CB,)1OI:1

0c tel-methylene glycol H 0 C Hi) l-OH Diethylene glycol HO-CH,-C H;OCH,,C;OH

Trietbyloue glycol I l HO-(CH2CH:O)z-C Hr-CHz- B 'Ietraethylene glycol HO-(CH1-CH,-O) ;ClI CH -Ol1 0-. mor p-dihydroxy benzene lit) (OJ-0 l-lSuch a polymerizable monomeric carbon compound thus has the generalformula 2 FO-H-C-O-R FO-E( DOll Polymerizable monomeric compounds havingthe general formula F-O-EO-DO il may be prepared by first reacting onemolecule of a dihydroxy compound listed in Table III with one moleculeof the monoc'nloride of FL half ester of one of the dibasic acids listedin Table I with one of the alcohols listed in Table II, or in some casesof the half ester itself. (For example, a molecule of allylchlorcarbonate, which has been prepared by reacting one molecuie ofallyl alcohol with a molecule of pliosgene. may be reacted with amolecule of diethylene glycol.) One molecule of the resulting productmay then be reacted with one molecule of th chloride of acrylic,methacrylic or alpha-chloracrylic acid or in some cases of the aciditself.

Polymcrizable monomeric compounds having the general formula R-o--r---o--B ri-o-n include the diallyl ester of lactic-carbonate and thediallyl ester of hydroxy-aceto-carbonate. Other compounds having thisgeneral formula, as well as polymerizable monomeric compounds having thegeneral formula 0 F-O-B-ll-O-Jl may be prepared by reacting One moleculeof an ester of an alcohol listed in Table II. with a monobasichydroxy-substituted, chloro-substituted or bromo-substituted acid, suchas glycolic acid, chloracetic acid, lactic acid, alpha-bromo propionicacid or hydroxy benzoic acid, (e. a. allyl lactate or crotyl lycolate)with One molecule of a. derivative of acrylic, methacrylic oralpha-chloracrylic acid or with one molecule of a derivative of a halfester of one of the dibasic acids listed in Table I with one of thealcohols listed in Table II. In the case of the first nine dibasic acidslisted in Table I, the half ester may also be a half ester of methyl,ethyl, pron isopropyl, n-butyl, isobutyl, secondary hutyl tertiary butylalcohol.

Polymerizable monomeric compounds harlir: the general formula include:diallyl ethylene glycol dioxalate, diallyl ethylene glycol dicarbonate,diallyl diethylene glycol dicarbonate, diallyl trimethylene glycoldicarbonate, diallyl ethylene glycol disuccinatc, diallyl ethyleneglycol diadipate, diallyl diethylene glycol dimaleate, dimethallyldicthylene glycol dicarbonate, diallyl diethylene glycol dimalonate,2-(oxycarballyloxy) ethyl ethyl fumarate and 2-(oxycarbomethallyloxy)ethyl methyl fumarate.

The polymerizable monomeric carbon compound may also consist of an esterof a molecule of any of the dibasic acids listed in Table I with twosimilar molecules (or a mixed ester of a molecule of such a dibasic acidwith two dissimilar molecules) each of which is an ester of glycolic,lactic or o-, m or p-hydroxy benzoic acid with any of the alcoholslisted in Table II. Such a polymerizable monomeric carbon compound hasthe general formula place of lactic, gylcolic or 0-, mor p-hydroxybenzoic acid, so that the general formula is then Such monomericcompounds include: carbonyl bis(allyl lactate) '17 bonyl bis(allylglycolate), carbonyl bis(allyl salicylate) and oxalyl bis(allylglycinate).

The polymerizable monomeric carbon compound may also consist of an etherof two similar or dissimilar molecules each consisting of an ester ofglycolic, lactic r 0-, mor p-hydroxy benzoic acid with any of thealcohols listed in Table II. Such a polymerizable monomeric carboncompound has the general formula Monomeric compounds having this generalformula include: the esters of alcohols listed in Table II withdiglycolic acid, with diethyl ether alpha, alpha'-dicarboxyllc acid, orwith any diphenyl ether dicarboxylic acid in which each of the benzenerings has one carboxyl group attached to it. In the preparation of sucha compound, an ether of two hydroxy-substituted acid molecules may firstbe prepared by reacting the sodium derivatives of glycolic, lactic orany hydroxy-benzoic acid with chloracetic or alphachlorpropionic acid inaccordance with the usual procedure for preparing ethers. may then beesterified with any of the alcohols listed in Table II. If it is desiredto prepare a compound of this type whose molecule is an ester of twodifferent alcohols, it may be more convenient to prepare an ester of oneof the alcohols listed in Table II with glycolic, lactic orhydroxy-benzoic acid, and then to react the sodium derivative of suchester with the ester of a different alcohol listed in Table II andchloracetic or alpha-chlorpropionic acid, to form the ether linkage.

The polymerizable monomeric carbon compound may also consist of an etherof a molecule of ethylene glycol, propylene glycol, 1,2-butylene glycol,2,3-butylene glycol or 0-, mor p-dihydroxy benzene with two similar ordissimilar molecules each consisting of an ester of glycolic, lactic or0-, mor p-hydroxy benzoic acid with any of the alcohols listed in TableII. Such a polymerizable monomeric carbon compound has the generalformula A compound having the general formula may be prepared byreacting one molecule of a sodium derivative of ethylene, propylene or abutylene glycol or of a hydroxy benzene with two molecules of an esterof chloracetic acid or alpha-chloropropionic acid with one of thealcohols listed in Table II, in accordance with the usual procedure forpreparing others. If an unsymmetrical compound having this generalformula is desired, one molecule of the ester of chloracetic oralpha-chloropropionic acid may be reacted with one molecule of thesodium derivative and the product may then be reacted with one moleculeof a different ester of such an acid. As an alternative method, onemolecule of the dichloro or dibromo compound corresponding to ethylene,propylene or a butylene glycol may be reacted with two molecules of thesodium derivative of the ester of glycolic, lactic or a hydroxy benzoicacid with one of the alcohols listed in Table II.

The polymerizable monomeric compound may also consist of an ester of amolecule of silicic acid with four molecules of an ester of glycolic Theproduct 18 or lactic acid with any of the alcohols listed in Table II.Such a polymerizabie monomeric carbon compound has the general formula 0o o 0 mild LILH in which I) is methylene or methyl methylene and R hasthe same significance as before. Such compounds include tetra(allylglycolate) silicate and tetra allyl lactate) silicate.

PREPARATION or STABILIZED Gourosrrrozv In a stabilized thermosettingcomposition of the present invention containing a filler, the proportionof filler to polymerizable binder (i. e., polymerizable unsaturatedpolyester or mixture thereof with a polymerizable unsaturated monomericcompound or with other substances which may or may not be polymerizable)varies with the specific characteristics of the binder and filler andwith the desired physical form of the composition.

In general, the proportion of an organic filler may range from 0 toabout 75 per cent of the thermosetting composition. (As used herein theterms "per cent and parts" mean per cent and parts by weight unlessotherwise designated.) Usually, when an organic filler is used, it ispreferable that the proportion be within a range of about 50 to per centof the composition, and it is most desirable that it be about 60 percent of the composition. The proportion of an inorganic filler may rangefrom 0 to about 55 per cent of the thermosetting composition. but whenan inorganic filler is used, it is usually preferable that it be withina range of about 60 to per cent of the composition. However. theseranges vary with the specific characteristics of the polymerizablebinder in the composition.

The proportion of filler may be as large as it is possible to employwhile still permitting the material to be held together by the binder inthe form of a coherent finished article. The maximum proportion offiller that can be employed depends upon the absorbency of the filler,because an absorbent filler reduces the apparent proportion of binder byabsorbing more of the binder.

As hereinbefore stated, from the standpoint of economy of time and moneyit is desirable that a thermosetting composition when received by theuser contain a catalyst that promotes rapid polymerization of thecomposition at molding temperatures. However, a curing catalystincorporated in a thermosetting composition in an amount suiiicient tocause the composition to cure completely at molding temperatures so asto produce fully cured molded articles, in the absence of a stabilizerhas the effect of promoting polymerization at atmospheric temperaturesto such an extent that after storage for short periods the compositionbecomes a substantially infusible, worthless mass that cannot be formedinto any useful product. Even during shipment such a thermosettingcomposition may become at least partially set up so that it iscontaminated with hard spots of polymerized material. A few hard"stones" or procured granules may damage an expensive mold, and also maycause 19 defective spots in pieces molded from such material which arereadily apparent even to an inexperienced observer. Such spots make amolded piece unsatisfactory for commercial use.

The use of a smaller amount of curing catalyst than is normally requiredfor complete cure at molding temperatures may be eilective in preventingpolymerization of the composition to an infusible worthless mass duringstorage or shipment. However, there is a proportionate loss in the waterresistance, strength, electrical properties and general quality ofarticles molded from the composition. During storage some of thecatalyst, which is in a reduced proportion to start with, appears todecompose so that the curability becomes progressively worse until thecomposition becomes a worthless unpolymerizable mass. The addition of aninhibitor in place of omission of part of the catalyst has the sameundesirable efiect-when an ordinary inhibitor is used in an amountsufiicient to prevent polymerization of the composition at atmospherictemperatures to an iniusible worthless rnass, the inhibiting actionremains in effect during fabrication of articles from the compositionand interferes with polymerization during fabrication. During stora e ofthe composition over a period of time the inhibitor in effect uses up"the catalyst so that the composition eventually becomes a worthlessunpolymerizable mass.

A thermosetting composition embodying the invention having incorporatedtherein a curing catalyst is stable at atmospheric temperatures becauseit contains a stabilizer (as hereinbefore defined). A thermosettingcomposition embodying the invention is "stable during storage underordinary conditions for a given period in that it meets both of thefollowing conditions during that period: (1) the composition neitherpolymerizes to a hard unusable mass nor develops appreciable lumps orhard centers which will produce defective spots in pieces molded fromsuch material and (2) the composition retains its plasticity andcurability so that it can be molded into pieces having a, cured qualitythat is unimpaired by such storage (1. a, the composition curescompletely at molding temperatures in a very short time to hard piecesthat are resistant to water and to deterioration and cracking from heat,etc).

A composition embodying the invention is sta ble for over two months.This means that when the material has been stored at atmospherictemperatures [or two months it is soft and free from "hard centers orprecured granules that damage the mold, and can be molded into pieceshaving a cured quality that is unimpaired by such storage. Duringstorage after two months hard lumps of material may start to form and/orthe cur-ability oi the material may start to decrease, but the materialmay still be quite satisfactory for commercial use for three months ofstorage. After three months of storage the ma terial may not be stable.i. e., hard centers or procured granules may develop sufficiently tocause defective spots in a molded piece that make the pieceunsat'sfactory for commercial use, and/or the curability of the materialmay decrease to such an extent that the cured quality of the moldedmaterial is not good enough for it to be considered commercially useful.

A thermosetting composition embodying the invention rarely polymerizesduring storage at atmospheric temperatures to a hard worthless mass.Instead it may become unstable" because the curability of the materialdecreases. When the stability fails after a. long period of storage byreason of loss of curability. such loss of cura bility may be due to thefact that the catalyst starts to decompose after such a period, so thatthe material does not cure properly because the proportion of curingcatalyst is too low. A composition which does not contain a stabilizerand contains instead such a small amount of catalyst that polymerizationdoes not occur at atmospheric temperatures would fail by reason of lossof curability after a shorter period, because the catalyst proportion isless to start with.

The proportion of curing catalyst used in the practice of the inventionis simply the proportion that causes the composition to polymerize atthe desired rate, and, as the term catalyst" implies, such proportion isthe usual catalytic amount, 1. e., ranging from about 0.01 per cent toabout 5 per cent of the polymerizable binder. It is ordinarily notdesirable to use a concentration of catalyst larger than about 5 percent of the polymerizable binder in an attempt to increase thecurability at molding temperatures, because beyond a certainconcentration, which varies for specific catalysts, the catalytic effectno longer increases and remains approximately constant. There is also agreater tendency for 'a composition containing an excess of curingcatalyst to polymerize at atmospheric temperatures, so that unless theamount of stabillr used in a thermosetting composition embody; theinvention to prevent curing of the coir; sition at atmospherictemperatures is also creased, the stability of the composition will 1::reduced. Furthermore, it is wasteful to use a large excess of curingcatalyst because the rate of decomposition of the catalyst appears toincrease with its concentration, so that the greater the amount ofcatalyst the more rapidly it appears to be lost during storage.

The preferred proportion of curing catalyst varies with difierentcatalysts, and the amount of a specific curing catalyst required toproduce a given rate of hardening may vary also with variations in thenature of the polymerizable composition. Benzoyl peroxide, which ispreerred in the practice of the present invention, is desirably used ina concentration ranging from about 1 to about 3 per cent of thepolymerizable binder.

The proportion of stabilizer in a thermosetting composition embodyingthe invention must be large enough to make the composition sufficientlystable at atmospheric temperatures to be commercially useful, but mustnot be so large that an inhibiting efiect is produced at moldingtemperatures. That is, when too large an amount of stabilizer ispresent, polymerization of the composition is retarded at atmospherictemperatures, but there is a proportionate decrease in the curability atmolding temperatures. When the material is heated during fabrication tothe temperatures at which polymerization is usually carried out, e. g.,250 to 300 degrees F., the eiiect of the stabilizer is overcome providedthere is not too much stabilizer present. Apparently at room temperaturethe stabilizer either prevents the formation of free radicals whichmight initiate polymerization, or prevents free radicals from activatingthe unsaturated compounds. At high temperature the stabilizer is notefiective against the free radicals, so that while a thermosettingcompositlon may be stable at atmospheric temperatures, it suffers noloss of curability at molding temperatures. However, when too muchstabilizer is present it may be sufficiently active at moldingtemperatures to destroy too many free radicals, so that the durabilityis reduced.

The proportion of stabilizer in a thermosetting composition embodyingthe invention may vary in accordance with the stability required of thecomposition. Ordinarily the proportion of stabilizer is such as topermit the composi tion to remain "stable" (as hereinbeiore defined) atatmospheric temperatures for approximately two months or more.Thermosetting compositions which are stable for periods shorter than twomonths are not considered to be commercially useful. Thus, the maximumproportion of stabilizer in a thermosetting composition is that which isso large as to affect seriously the cured quality of the compositionafter two months storage at atmospheric temperatures. so that thecomposition is not stable" (as hereinbefore defined) after two months.The minimum proportion of stabilizer is that which is so small as to beineffective in retarding the polymerization of the composition after twomonths storage at atmospheric temperatures without a proportionatedecrease in curability, so that the composition is not stable after twomonths. In general, the proportion of pbenzoquinone used in the practiceof the present invention is not less than approximately .08 per cent ofthe polymerizable binder, and preferably is not less than about .15 percent of the polymerizable binder. The proportion of this stabilizer usedis not more than approximately .3 per cent of the polymerizable binderand preferably is not more than about .25 per cent of the polymerizablebinder. However, these range only indicate the practical proportions ofp-benzoquinone that may be used to prepare a stabilized thermosettingcomposition embodying the invention containing the amount of curingcatalyst ordinarily used and containing a polyester having ordinaryproperties. For example, although use of a stabilizer in the minimumamount indicated ordinarily gives a composition having a stability of atleast two months. with a large amount of catalyst the stabilizer mighthave to be used in a larger proportion to produce the same stability; onthe other hand, when the polymerizable binder has relatively lesstendency to polymerize at atmospheric tem' peratures, the sameproportion of the stabilizer might produce a stability of longer thantwo months.

The stabilizing effect produced by p-benzoquinone differs with variouspolymerizable unsaturated monomeric substances, a here'inbeforedescribed, that may be present in the polymerizable binder. At moldingsuch a monomeric substance often seems to aid in overcoming thestability toward polymerization produced by the stabilizer atatmospheric temperatures. The stabilizer neutralizes or immobilizes freeradicals at atmospheric temperatures but is ineffective against the freeradicals at molding temperatures, so that it does not decrease thecurability of the composition at molding temperatures. The monomericsubstance copolymerizes with the unsaturated polyester through ethylenicdouble bonds by means of chain reactions initiated by the free radicalstemperatures 22 so that at molding temperatures the monomeric substanceaids in curing the composition.

The proportion of monomeric substance in the polymerizable binder thatmay be used in a thermosetting composition of the invention varies inaccordance with the physical form of the composition as well as with theproportion of pbenzoquinone employed. In general, when less than 2 percent of the polymerizable binder consists of a polymerizable monomericsubstance, the monomer may be ineffective in helping to cross-link thestraight chain polyester molecules at molding temperatures. Thus, it isdesirable that the monomer comprise at least 2 per cent of thepolymerizable binder, and the proportion of monomer may be as high as 98per cent of the polymerizable binder. It is usually preferable that atleast 20 to 40 per cent of the binder consist of a polymerizableunsaturated monomeric substance. A granular thermosetting compositionwhich contains a polymerizable binder that consists of approximately 10to 30 per cent of a polymerizable monomeric compound and about '70 toper cent of a polymerizable polyester produces a final polymerizedproduct that has excellent water resistance and insolubility.

In order to demonstrate the efiectiveness of p-benzoquinone which may beused in the preparation of a stabilized thermosetting compositionembodying the invention, the following test is conducted.

A polymerizaole binder, consisting of 23.6 parts of a polymerizableunsaturated polyester (prepared by esterifying 1.0 mol of ethyleneglycol with 0.2 mol of phthalic anhydride and 0.8 mol of maleicanhydride by the procedure hereinbefore described to an acid number of35) and 9.2 parts of a polymerizable unsaturated liquid monomer (diallylphthalate), is mixed in a Banbury mixer with 1.3 parts of "Luperco ATC"catalyst (a paste consisting of 50 per cent benzoyl peroxide and 50 percent tricresyl phosphate), 2 parts of a lubricant (zinc stearate), afiller consisting of as parts of clay and 20 parts of asbestos, and .065part of pbenzoquinone. The mixing is continued until a soft, homogeneousdough is obtained. The material is then removed from the mixer andformed into solid lumps about two inches in diameter. The lumps arecooled, and are then stored in closed containers at room temperature todetermine the length of time for which the material may be stored beforeit can no longer be considered stable (i. e., to determine the moldablelife of the material).

At intervals during storage, one lump of the putty-like material is cutthrough the center and examined for the presence of "stones" or hardcenters (hardening ordinarily occurs first in the center). Afterexamination of the centers, the lump so examined is extruded into a rodor ribbon about one-quarter inch thick, and the extruded material istested for cured quality by molding it in a small tumbler mold atordinary pressures e. g., 1000-2000 pounds per square inch of projectedarea). The small tumbler so molded weighs about 3 grams, and is 1 incheshigh, having a top diameter of 1% inches and a bottom diameter of If;inches.

For the sake of comparison, lumps of a control material that is the sameexcept that it contains no stabilizer are simultaneously prepared andtested by the procedure described hereinbefore. The results of the testsare shown in Table IV below in which X is the composition of theinvention and Y is the control. The figures repre- Table IV CompositionDay Stable The difference in the efiects produced in a thermosettingcomposition by a stabilizer used in the practice of the presentinvention i. e., pbenzoqulnone) and by a substance which acts as aninhibitor may be demonstrated by tests made as follows:

Three putty-like materials are prepared by the procedure last described,using a difierent amount of p-benzocuinone as the stabilizer in eachmaterial, as indicated in the second column of Table V. For the purposeof comparison three materials are prepared which are the same exceptthat, in place of the stabilizer, a corresponding amount of hydroquinoneis used, as indicated in the second column of Table V. Lumps of eachmaterial are placed in storage containers at 90 degrees F. and at 30 to50 per cent relative humidity, and are tested at intervals by theprocedure hereinbeiore described. (Such conditions are more extreme thanthe conditions to which the material ordinarily would be subjected. Atroom temperature the stability is, of course, much better. For example,the stability at 90 degrees F. of the composition described as a controlin Table IV is approximately seven to eleven days, in contrast to astability of one month at room temperature.) The results of the testsare shown in the third and fourth columns of Table V.

Table V l l l Substance Used Days Stable Remarks hydroqulnone .04 lest:than ll polymerizes in 11 days.

\ i oys. p-henzoouinone M .04 l 35 days..... alter 35 days material hasnot polymerized l and cured quality is satisfactory. hyrlrnqumone... l1155 less than ll cured quality is un- 1 days. satisfactory ii'lli'n l11 l days. p-bcnzoouiuonc [9% days.. after 55 days Imperial 1 has notpolymerized l l and cured quality is i salisfactory. hydroquinnnc. .08illldays cured quality is seriously afiectcd after ludays.p-benznqnmond. 5 .08 l I?! days after 63 days nuitcrial I has notpolymerized i but cured quality is i no longer satisfac- 1 tory.

The results in Table V not only illustrate the effect of varying theproportion of p -benzoquinone in a. thcrmosetting composition embodyingthe invention but also illustrate the properties that distinguishp-benzoquinone from an ordinary inhibitor. A substance that is astabilizer (p-benzoquinone) retards the polymerization of athermosetting composition at atmospheric temperatures withoutproportionately decreasing its curability for a considerable period oftime which varies in accordance with the proportion of stabilizer. Asubstance that is not a stabilizer has one of the following undesirableeffects on a thermosetting composition within a relatively short perioddepending upon the proportion of such substance: 1. does not retardpolymerization; 2. seriously aiTects the curability and does not retardpolymerization; or 3. retards polymerization but impairs the curabilityproportionately.

In the preparation of a thermosetting composltion embodying theinvention the polymerizable binder, catalyst and stabilizer may be mixedwith a filler in the proper proportions to obtain a homogeneouscomposition having the desired consistency, i. 8., a soft dough, or amaterial having a leathery texture, etc. Mixing of a filler with theother ingredients may be carried out in any suitable mixing or kneadingapparatus, e. g., by using any commercial mixer or by milling the fillerinto the material on a rubber mill. Mixing may be carried out at roomtemperature it the binder is not too viscous. If the viscosity of thebinder is too great it may be necessary to warm the binder to reduce itsviscosity when it is mixed with the filler. In any case, it is desirableto mix the binder in a liquid state with the filler so that the fillerbecomes thoroughly mixed with the binder.

If the binder in a composition embodying the invention comprises aviscous polymerizable suir-- stance and a less viscous polymerizablesubstar the polymerization catalyst may be dissolved the less viscouspolymerizable substance bi" the two substances are mixed. Also, the pmerization catalyst may be dispersed in :1. fl. :l. as by grinding withthe filler in a ball-mill, be? r the filler is mixed with the binder. Afibrous filler may be impregnated with a solution or the polymerizationcatalyst in a volatile solvent and dried before the filler is mixed withthe binder.

The stabilizer ordinarily may be added to the polymerizable binder afterthe addition of the catalyst. If there is a tendency for the material topolymerize at mixing temperatures when the catalyst is added thestabilizer may be added before the catalyst or with the catalyst. Forexample, when a binder containing a hard polyester is used it must bewarmed in order to reduce its viscosity when it is mixed with a filler.Ordinarily during heating the composition containing a polymerizationcatalyst might polymerize. However. in the practice of the presentinvention the stabilizer that is added (before adding the catalyst orwith the catalystl functions to prevent polymerization during mixing. aswell as during storage at atmospheric temperatures. of a thermosettingcomposition containing a polymerization catalyst.

Usm A8 A LAMmA'rm Coirrosrrlox Although the foregoing discussion of thestability of compositions embodying the invention has referred primarilyto stabilized compositions embodying the invention which contain afiller and which may be used as molding compositions, a stabilizer usedin the practice of the invention has been found to be extremelyefiective in extending the liquid life of thermosetting compositionsembodying the invention which are used as laminating resins. Forexample, a stabilizer used in the practice of the invention in theamounts hereinbefore described is effective in preventing gelling of alaminating resin comprising 25 a polymerizable binder and a catalyst, ashereinbefore described, for at least one month. A laminating resin whichhas a liquid life of one month, i. e., a resin which does not gel uponstorage at atmospheric temperatures for one month, is advantageous forcommercial use.

A laminating composition of the invention containing catalyst andstabilizer may be brushed or sprayed onto the material to be laminated(or the material may be dipped into a solution (e. g., a 50 per centacetone solution) of the laminating resin), and the sheets of thematerial may be air-dried before assembling and curing under pressure byany of the procedures ordinarily employed in the production oflaminates.

Use AB A Mounno COMPOSITION A composition comprising a polymerizablepolyester is highly advantagcous for the molding of articles underpressure. Since a polymerizable polyester is fusible and plastic at arelatively low temperature, it is possible to adjust the amounts ofcatalyst and stabilizer so that hardening at such a temperature takesplace at a reasonable rate to allow ample opportunity for shaping andmolding oi the composition. Shaping and molding may be completed at sucha temperature, and the shaped composition may then be held at the sametemperature while slow hardening takes place, or may be heated to ahigher temperature to cause quick hardening. These properties are incontrast to those of urea-formaldehyde, melamine-formaldehyde andphenol-formaldehyde resins, which are plastic only at elevatedtemperatures at which they harden so rapidly that hardening interfereswith shaping.

Hardening of a polymerizable polyester can be carried out at atemperature that is far below the decomposition temperature of thepolyester and thus at a temperature at which discoloration does not takeplace. Other heat hardenable products, such as urea, melamineorphenol-formaldehyde products, must be heated much closer to theirdecomposition temperatures in order to cause hardening to take placeeven at moderate speed. When an attempt is made to harden such otherproducts rapidly by raising the hardening temperature, discoloration orburning is likely to result.

A polymerizable polyester may be fabricated in an injection moldingmachine. A supply of the polyester containing the curing catalyst may beheld in the supply cylinder of the machine at a temperature at which thecomposition is highly plastic but hardens very slowly, and the mold maybe held at a temperature at which the composition hardens rapidly. Undersuch conditions the mold may be filled rapidly from the supply cylinderby injection of the composition under pressure. The composition mayharden so rapidly at the temperature of the mold that the finishedhardened piece may be removed almost immediately after the mold has beenfilled. Thus very rapid automatic operation of the machine is possible.The main dilference between such an operation and the ordinary operationof injection molding; a thermoplastic material is that in the injectionmolding of the polymerizable polyester the mold is at a highertemperature than the supply cylinder, whereas in injection molding of athermoplastic material the mold is at a lower temperature than thesupply cylinder.

Thus a polymerizable polyester can be molded as economically as athermoplastic material. The

26 molding of other heat hardenable products is a much slower and moreexpensive operation than the molding of a thermoplastic material.

Care should be taken that any material incorporated in a compositionembodying the invention does not tend to cause the composition to set upduring its preparation or during storage (e. g., carbon black isundesirable for this reason). In the preparation of a moldingcomposition, plasticizers, lubricants, fillers, pigments and othercoloring matter maybe incorporated if desired.

The following examples illustrate the preparation of a stabilizedthermcsetting composition.

EXAMPLE 1 A polymerizable binder, consisting of 23.6 parts of apolymerizable unsaturated polyester (prepared by esterifying 12.5 molper cent of propylene glycol and 87.5 mol per cent of ethylene glycolwith 20 mol per cent of phthalic anhydride and 89 mol per cent of maleicanhydride by the procedure hereinbefore described to an acid number of35) and 9.2 parts of a polymerizable unsaturated liquid monomer (diallylphthalate), is mixed with 1.3 parts of "Luperco ATC" catalyst (a pasteconsisting of 50 per cent benzoyl peroxide and 50 per cent tricresylphosphate) and a stabilizer (0.2 part of p-benzoquinone) to obtain ahomogeneous liquid mixture. A 75 cc. sample of the laminating resin soprepared, in a 150 cc. test tube, gels after standing for 31 days atroom temperature, while another sample gels after standing for 25 daysat a temperature of 90 degrees F. A 75 cc. sample of a laminating resinprepared by a procedure that is the same except that the stabilizer isomitted gels after only 7 days in a 150 cc. test tube at roomtemperature, while another sample of the same resin gels after only 2days at a temperature of 90 degrees F.

EXAMPLE 2 A polymerizable binder consisting of 21.3 parts of apolymerizable unsaturated polyester (prepared by esterifying 20 mol percent of propylene glycol and mol per cent of ethylene glycol with 12.5mol per cent of phthalic anhydride and 87.5 mol per cent of maleicanhydride by the procedure hereinbefore described to an acid number of35) and 11.5 parts of a polymerizable unsaturated liquid monomer(diallyl phthalate), is mixed in a Banbury mixer with 1.3 parts ofLuperco ATC" catalyst, 2 parts of a lubricant (zinc stearate), a flllerconsisting of 48 parts of clay and 20 parts of asbestos, and astabilizer (.1 part of p-benzoquinone) The mixing is continued until asoft, homogeneous putty is obtained. Lumps (approximately two inches indiameter) of the material so prepared remain stable at degrees F. and at30 to 50 per cent relative humidity for approximately 68 days. Lumps ofa putty-like material prepared by a procedure that is the same exceptthat no stabilizer is added are stable under the same conditions forless than 11 days. Lumps of a composition prepared by a procedure thatis the same except that the amount of catalyst used is 1.98 parts arestable for over 90 days at room temperature. Similar results areobtained when an equivalent proportion of diethylene glycol is used inplace of the monoethylene glycol in the preparation of the polymerizableunsaturated polyester.

I claim:

A stabilized thermosetting composition, comprising (1), as a binder, acopolymerlzable mixture of a monomeric polyallyl ester and an un- 27saturated alkyd resin; (2) a. catalyst of the class consisting oforganic peroxides and organic ozonides, in an amount from 0.01 to 5 percent of the total weight of polymerizable binder; and (3) as an agentfor increasing the stability of the composition at atmospherictemperature without proportionately decreasing the curability of thecomposition, p-benzoquinone, in an amount from 0.08 to 0.3 per cent ofthe total weight of polymerizable binder.

THOMAS F. ANDERSON.

4D REFERENCES CITED Number UNITED STATES PATENTS Name Date Glick Dec.28, 1948 Loritsch Feb. 27, 195i

